184 



Prof. Sydney Young on the 



benzene are given in the following Table, together with the 

 molecular and specific critical volumes calculated from them, 

 taking the observed critical volume of fluorbenzene as correct. 

 For the sake of comparison the specific volumes directly 

 observed and also those previously adopted by Ramsay and 

 myself are given. 



Table XXII. 



Substance. 



Mean 

 Eatio. 



Molecular 

 Volume. 



Calculated. 



Specific Volume. 



Calculated. 



Observed. 



Earn say 

 and Young. 



C e H-F 



1-1246 



1-1802 



1-2772 



•944 



1-010 



1-290 



1-047 



•440 



•620 



•800 



•630 



262 

 275 



298 

 220 

 235 

 301 

 244 

 103 

 144 

 186 

 147 



2-34 

 1-76 

 1-47 

 2-83 

 1-53 

 1-16 

 3-30 

 3-21 

 315 

 3-11 

 2-45 



2-43 

 2-34-245 



2*82 



2-46 



4 : 06 

 3-7 

 3-5 

 3(5 



CgH-Cl 



(LH-Br 



C 6 H-I 



C r H R 



CC1 4 



Sn01 4 



(O a H 5 ) a O 



CH 3 OH 



C 2 H 5 OH 



C 3 H 7 OH 



CH3COOH ... 



It will be seen that the values for benzene and acetic acid, 

 calculated from the mean ratios, agree very well with those 

 directly observed, and this may be taken as evidence in favour 

 of the accuracy of the method of direct measurement adopted. 

 On the other hand, the calculated values for ether and the 

 alcohols are considerably lower than those previously given 

 by Ramsay and myself. But it may be pointed out that the 

 critical temperature of ether was almost certainly slightly 

 underestimated, owing to the employment of the vapour of 

 methyl salicylate as a jacket. There is no reason to suspect 

 any error in the determination of the critical pressure ; and 

 if the constants for Biot's formula be taken as correct, the 

 calculated temperature corresponding to the critical pressure 

 would be 194*4 instead of 193*8, and the higher value agrees 

 well with a more recent determination by Ramsay, who in 

 this case employed the vapour of quinoline as a jacket. The 

 correction of the critical temperature of ether would give a 

 lower value to the critical volume. 



Again, Professor Tait has recently made an exhaustive 

 mathematical investigation of the relations of pressure, tem- 

 perature, and volume of several substances, including ether, 



